Apparatus and method for reducing the strength of an electrostatic field in an oil tanker using ionized gas

ABSTRACT

The apparatus and method permits the electrostatic field strength of a charged mist in a substantially empty hold of a tanker to be reduced safely. The apparatus includes a manifold having nozzles receiving a supply of air at a predetermined location in the hold of the tanker. The nozzles are designed in such a manner that the air leaving each nozzle is ionized to a polarity opposite to the polarity of the charged mist and is distributed throughout the hold of the tanker. The distributed ionized gas effectively reduces the strength of the electrostatic field except for a low residual field within safety limits.

United States Patent [1 1 Dancy BEST AVAILAB 8 1 July 15,1975

1 1 APPARATUS AND METHODFOR REDUCING THE STRENGTH OF AN ELECTROSTATIC FIELD IN AN 01L TANKER USING IONIZED GAS [75] Inventor: Julian H. Dancy, Richmond. Va.

[73] Assignee: Texaco Inc., New York, NY.

[22] Filed: Aug. 23, 1973 [21] Appl. No.: 390,804

[52] US. Cl 317/2 R; 239/3; 239/15 [51] Int. Cl. 1105f 3/00 [58] Field of Search 239/15, 3; 317/2 R, 2 D, 317/2 E; 118/629, 621, 627; 134/10, 22 R, 24

[56] References Cited UNITED STATES PATENTS 632,185 8/1899 Jones 317/2 R (X) 1,854,475 4/1932 Littlefield 239/3 3,121,027 2/1964 Galanor 134/10 3,296,491 l/1967 Brown 239/15 (X) 3,297,281 1/1967 Felici 239/15 (X) 8/1972 Roberts 317/2 R (X) 4/1974 Buser et a1 239/15 5 7 ABSTRACT The apparatus and method permits the electrostatic field strength of a charged mist in a substantially empty hold of a tanker to be reduced safely. The apparatus includes a manifold having nozzles receiving a supply of air at a predetermined location in the hold of the tanker. The nozzles are designed in such a manner that the air leaving each nozzle is ionized to a polarity opposite to the polarity of the charged mist and is distributed throughout the hold of the tanker. The distributed ionized gas effectively reduces the strength of the electrostatic field except for a low residual field within safety limits.

8 Claims, 2 Drawing Figures 29 2e FILTER 6g,

(HOLD or TANKER Field ofz the Invention APPARATUS ANDMETHOD. FOR REDUCING. THE

STRENGTH, OF AN ELECTROSTATIC FIELD IN AN on. TANKERUSING IONI'ZEDGAS 1 1 BACKGROUND OFYTI-IE INVENTION The presentpinvention relates to apparatus :and

method for reducing the strength of an electrostatic .volume. The apparatus comprises a source-providing a gas at a predetermined pressure at a'predetermined lo-: cation in the enclosed volume in a manner so that the gas is ionized and acquiresa charge opposite in polarity to the polarity of the electrostatic field of .the initial mist. The ionized gas is distributedthroughout the enclosedvvolume so that the net'strength of the electrostatic field is substantially less than'thestrength'of the electrostaticfield-of the initial mist.

The objects and advantages of the invention will'a'ppear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein one embodiment of the aforementioned invention is illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustration purposes only and are not to be construed as defining the limits of the invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 depicts apparatus, constructed in accordance with the present invention, for substantially reducing the strength of an electrostatic field of a charged mist in a hold of a tanker.

FIG. 2 is a detailed drawing of a nozzle shown in FIG. 1.

DESCRIPTION OF THE INVENTION In recent years several mammoth oil tankers have experienced explosions. The most probable cause of the explosions has been traced to the existence of a mist, having an electrostatic field, in a substantially empty hold of a tanker, resulting from tank washing activities and a subsequent electrical discharge of that field in the presence of an explosive atmosphere. The apparatus and method of the present invention combines ionized gas, having an electrostatic charge of opposite polarity to the field, with the mist to substantially reduce the net strength of the electrostatic field of the mist to a level such that a subsequent discharge, if any, will not cause an explosion.

Referring now to FIG. 1, there is shown a field reduction system. A manifold 1, having nozzles 3, is lowered into the hold of a tanker through one of several openings, generally available, to a predetermined depth. For large holds several manifolds with nozzles may be used simultaneously at different locations in the holds. A nozzle 3 is shown in greater detail in FIG. 2.

A supply 28 of air provides air to a conventional type air filter 29 which filters out particles from the air to prevent clogging of nozzles 3. The air pressure is not critical and, as such, no regulator is required. Generally, the tanker has a compressed air line which may be used as supply 28. The air from filter 29 is provided to manifold which in turn provides the-lair to each nozzle Referring to FIG. 2, :nozzle 3, includes a housing 40 which may be a copper fitting having one end sealed.

A brassrod 42 is embedded in the conductive, sealed end ofhousing 40 in a'mannertso that it extends along a center axis of housing which passes through-the sealed end and a second-end opposite the sealed end of housing 40. A thin wire 45 is affixed'to rod 42 so that it extends along the center axis'and passes through the second end of housing 40 and through a copper tube 47. Copper tube 47 has a predeterminedlength-:and is affixed to the housing 40.-=The open end of tube 47 is rolled to provide an orifice 48.

Nozzle'3 is mounted to conductive'manifold '1 by a threadedthir'd end of housing 40. The air is provided through the third endof housing 40-and-passes through orifice 48 to become a stream of air passing over wire 45. Wire 45 is connected electrically to a groundx through rod 42, housing 40 and its sealed end; manifold 1 and conductor 56 connecting manifold 1 to ground When nozzle 3 is placed in an electrostatic field, with no air being supplied to it, the-air surrounding wire'45 develops a space charge, or another way of stating the occurrenceis that the gas in the immediate vicinity of wire 45 is ionized. The space charge is of an opposite occurrence is to the polarity of the charged mist. Gradually, the corona current in wire 45 going to ground will decrease, as the space charge builds up until the charge no longer nolonger increase.

By supply air to housing 40, the ionized gas is blown away allowing wire 40 to ionize more air. The ionized air mingles with the electrostatically charged mist so that the apparent charge of the new combination is substantially less than the charge of the original mist.

Referring again to FIG. 1, manifold 1 may be a length of brass pipe having tapped holes at predetermined intervals to facilitate the mounting of nozzles 3. The design of manifold 1 is determined by the volume to be filled with ionized air. Manifold 1 can carry fifteen nozzles 3, which are mounted in groups of three. The direction of discharge of nozzles 3, for one group is opposite to the direction of discharge for an adjacent group of nozzles 3 to reduce the rotational effect imparted to manifold 1 by the discharging air from nozzles 3. N02- zles 3 are spatially arranged with manifold 1 so as to achieve the maximum distribution of the ionized air.

The combined strength of the electrostatic field of the mist and ionized air is substantially less than the strength of the electrostatic field of the mist.

The apparatus of the present invention as heretofore described ionizes and distributes a gas in the presence of an electrostatic field of a charged mist in such a manner so that the ionized gas assumes an opposite polarity to the polarity of the electrostatic field of the mist. The net strength of the electrostatic field is reduced to a safe value, thus eliminating the probability of an explosion due to the accidental discharge of the electrostatic field.

What is claimed is:

1. Apparatus for reducing the strength of an electrostatic field of a charged mist in a substantially enclosed volume, comprising means for providing a supply of a non-explosive gas at a predetermined location in the volume, means connected to the supply means for discharging the gas into the volume in a predetermined means for utilizing the electrostatic field of the charged "mist to ionize the gas, so that the ionized gas has a polarity opposite the polarity of the charged mist as the gas is discharged so that as the ionized gas mingles with the charged mist the net electrostatic field strength of the combined charged mist and ionized gas is substantially less than the electrostatic field strength of the mist prior to mingling with the ionized .gas.

2. Apparatus as described in claim 1 inwhich the gas is arr.

3. Apparatus as described in claim 2 in which the discharging means includes a manifold having plurality of openings and receiving air from the supply means, and a plurality of nozzles having orifices mounted at different predetermined angles on the manifold at the openings so as to discharge the air from themanifold through the orifices. I

4. Apparatus as described in claim 3 in which the utilizing means includes means for grounding the manifold and the nozzles. I

5. A method for reducing the strength of an electrostatic field of a charged mist in the hold of a petroleum tanker which comprises the steps of providing a supply of a non-explosive gas at a predetermined location in :the hold of the tanker, discharging the gas in the hold of the tanker in a predetermined manner. utilizing the electrostatic field of the charged mist to ionize the gas as it is discharged so that the ionized gas has a polarity opposite the polarity of the mist so that the ionized gas mingles with the charged mist and the net electrostatic field strength of the combined charged mist and ionized gas is substantially less than theelectrostatic field strength of the mist prior to mingling with the ionized gas.

6. A method as described in claim 5 in which the gas is air. v

7. A method as described in claim 6 in which the discharging step includes discharging theair through orifices of nozzles at a plurality of locations in the tankers hold in a manner to facilitate mingling of the ionized air and charged mist.

8. A method as described in claim 7 inlwhich the ion izing step includes ionizing the air as it leaves each nozzle'using a wire mounted in each nozzle and extending out of the nozzle a predetermined distance, and

grounding the wire.

I l s 

1. Apparatus for reducing the strength of an electrostatic field of a charged mist in a substantially enclosed volume, comprising means for providing a supply of a non-explosive gas at a predetermined location in the volume, means connected to the supply means for discharging the gas into the volume in a predetermined manner, and means connected to the discharging means for utilizing the electrostatic field of the charged mist to ionize the gas, so that the ionized gas Has a polarity opposite the polarity of the charged mist as the gas is discharged so that as the ionized gas mingles with the charged mist the net electrostatic field strength of the combined charged mist and ionized gas is substantially less than the electrostatic field strength of the mist prior to mingling with the ionized gas.
 2. Apparatus as described in claim 1 in which the gas is air.
 3. Apparatus as described in claim 2 in which the discharging means includes a manifold having plurality of openings and receiving air from the supply means, and a plurality of nozzles having orifices mounted at different predetermined angles on the manifold at the openings so as to discharge the air from the manifold through the orifices.
 4. Apparatus as described in claim 3 in which the utilizing means includes means for grounding the manifold and the nozzles.
 5. A method for reducing the strength of an electrostatic field of a charged mist in the hold of a petroleum tanker which comprises the steps of providing a supply of a non-explosive gas at a predetermined location in the hold of the tanker, discharging the gas in the hold of the tanker in a predetermined manner, utilizing the electrostatic field of the charged mist to ionize the gas as it is discharged so that the ionized gas has a polarity opposite the polarity of the mist so that the ionized gas mingles with the charged mist and the net electrostatic field strength of the combined charged mist and ionized gas is substantially less than the electrostatic field strength of the mist prior to mingling with the ionized gas.
 6. A method as described in claim 5 in which the gas is air.
 7. A method as described in claim 6 in which the discharging step includes discharging the air through orifices of nozzles at a plurality of locations in the tanker''s hold in a manner to facilitate mingling of the ionized air and charged mist.
 8. A method as described in claim 7 in which the ionizing step includes ionizing the air as it leaves each nozzle using a wire mounted in each nozzle and extending out of the nozzle a predetermined distance, and grounding the wire. 